Many different types of position sensors have been implemented in commercial, industrial and consumer applications. Some position sensors are intended to detect the movement of a target along a linear path while others detect the rotation of a target, such as a gear with a plurality of teeth, about an axis of rotation. The target and sensor can be arranged so that the target is provided with a plurality of magnetic poles that are sensed by a magnetically sensitive component. Alternatively, the sensor may be provided with a biasing magnet and the target can comprise a plurality of ferromagnetic discontinuities, such as gear teeth, that are sensed by the device.
One particular type of position sensing device is based on quadrature sensing, which involves the use of two signals that are offset from each other by 90 degrees so that a comparison of the signals will provide meaningful information with regard to the position of a target. Quadrature sensors generally provide two outputs that are 90 degrees out of phase. The rising and falling edges, of the output signals are generally utilized to determine the speed while the phase shift between the two output signals indicates direction of movement or rotation of the target. The two outputs can be obtained from two sensing elements that are physically spaced at a set distance to match an application-specific target.
The spacing of the sensing elements with respect to one another and the absolute placement of the sensing elements within the sensor package are critical to sensor's proper functioning. Maintaining the placement of the individual sensing elements often requires significant mechanical keying that is costly and inaccurate. Such mechanical features may also need to be recreated for each application. The physical size of the two sensing elements and associated mechanical features also limits how small the overall sensor can be made.